1. Field of the Invention
Apparatuses consistent with the present invention relate to a plasma accelerating, and more particularly, to a plasma accelerating apparatus and a plasma processing system having the same, which are used for semiconductor substrate processing for etching and removing a thin film from a substrate or depositing the thin film on the substrate.
2. Description of the Related Art
In recent years, with the increased need for high speed microprocessors and high recording density memories, techniques for reducing a thickness of a gate dielectric substance and a lateral size of a logic element has been actively developed so that many elements can be mounted on one semiconductor chip. There are techniques for reducing a gate length of a transistor to less than 35 mm, a thickness of a gate oxide to less than 0.5 nm, or improving a metallization level greater than 6 as examples of the aforementioned techniques.
However, in order to embody such techniques, high performance deposition and/or etching devices capable of increasing a mounting density of a device at the time of a manufacturing process of the semiconductor chip, have been required. Among the high performance deposition and/or etching devices, a plasma etcher or a plasma sputtering system using a plasma accelerating apparatus has been widely used.
FIG. 1 is a schematic cut-away perspective view showing a Hall effect plasma accelerating apparatus 10 used for a plasma etcher or a plasma sputtering system as an example of a conventional plasma accelerating apparatus. The Hall effect plasma accelerating apparatus 10 is disclosed in U.S. Pat. No. 5,847,593.
With reference to FIG. 1, the Hall effect plasma accelerating apparatus 10 includes a circular channel 22 having an upper shielded end and a lower open end. An internal circle coil 16, and external circle coils 17, 18, 18′, and 19 are coaxially positioned at an inside and an outside of the circular channel 22 in a line. The circle coils 16, 17, 18, 18′, and 19 have physically and magnetically isolated polarity so as to form a magnetic field. A circular anode electrode 24 is connected to a gas supply pipe 25 and ionizes a supplied gas. A cathode electrode 27 is positioned on a magnetic pole of a lower end of channel 22, is connected to the gas supply line 29, and supplies electrons. The external circle coils 17, 18, 18′, and 19 are divided into an upper coil 17 and lower coils 18, 18′ and 19 of separated sections. Encircling an outside of the channel 22 is the upper coil 17 and encircling an opening of the channel 22 are the lower coils 18, 18′ and 19. Upper portions of the upper coil 17 and the internal coil 16 are isolated by a dielectric layer 23. A magnetic field of the isolated region is shielded, so that a partially magnetic field intersecting a space portion 20 of the channel 22 is induced at only a region of an opening 22a of the channel 22, but not at an entire portion of the channel 22. A magnetic field formed at positions of the lower coils 18, 18′ and 19 partially captures electrons.
Consequently, the Hall effect plasma accelerating apparatus 10 may accelerate only positive ions but not an electrically neutral plasma by a magnetic field formed due to presences of the anode electrode 24 and the cathode electrode 27. Furthermore, the Hall effect plasma accelerating apparatus 10 laminates a charge on a surface of a substrate on which ions are deposited, causing a loss like a charge shunt and notching occurs in a minute pattern that may lead to a formation of a non-uniform etching profile.
FIG. 2 is a cross-sectional view showing a coaxial plasma accelerating apparatus 40 used for a plasma sputtering system or a plasma etcher as another example of a conventional plasma accelerating apparatus. The coaxial plasma accelerating apparatus 40 is disclosed in the article by J. T. Scheuer, et. al., IEEE Tran. on Plasma Sci., VOL. 22, No. 6, 1015, 1994.
Referring to FIG. 2, the coaxial plasma accelerating apparatus 40 includes a circular channel having an upper shield end and a lower open end. The circular channel 50 accelerates plasma produced by the discharging of an internally introduced gas. A cylindrical cathode electrode 54 is positioned inside the channel 50. A cylindrical anode electrode 52 is positioned at an outer side of an opening of the channel 50, which is coaxially spaced apart from the cylindrical cathode electrode 54 by a predetermined distance. In addition, the coaxial plasma accelerating apparatus 40 includes a control coil 64, a cathode coil 56, and an anode coil 58. The control coil 64 controls plasma in the channel 50. The cathode coil 56 is provided inside the cathode electrode 54. The anode coil 58 is provided outside the anode electrode 52.
The coaxial plasma accelerating apparatus 40 shown in FIG. 2 generates an electric current flowing through the channel 50 and induces a radial magnetic field enclosing the cathode electrode 54 by the current generated by including a channel 50 and a control coil 64. Here, the channel 50 has inner and outer walls in which the anode electrode 52 and the cathode electrode 54 are provided, respectively, and the control coil 64 is provided at an outside of the channel 50. In the coaxial plasma accelerating apparatus 40, a speed of plasma ions at an outlet port is very high, for example, about 500 eV. Further, a direct current discharge by an anode electrode and a cathode electrode is used, and thus plasma ions accelerated from the anode electrode 52 to the cathode electrode 54 collide with the cathode electrode 54 in the channel 50. However, the cathode electrode 54 is significantly damaged by such collisions and becomes difficult to use for an etching process of a semiconductor thin film deposition process.
In order to address the aforementioned problems, and other problems, an inductively coupled discharge type plasma accelerating apparatus 60 has been suggested as shown in FIG. 3 and FIG. 4. With reference to FIG. 3, the inductively coupled discharge type plasma accelerating apparatus 60 includes a plasma channel 77, an upper circle loop inductor 79, an internal circle loop inductor 71, and an external circle loop inductor 73.
A gas is ionized and accelerated in the plasma channel 77. The plasma channel 77 has a doughnut shape, which includes a downward open outlet port 77a. The outlet port 77a communicates with a process chamber (not shown) of a plasma etcher or a sputtering system of the plasma accelerating apparatus 60. An upper circle loop inductor 79 is disposed at an end wall 81 of the plasma channel 77. The upper circle loop inductor 79 applies radio frequency (“RF”) energy to the gas in the plasma channel 77 to generate electrons. The generated electrons collide with neutral atoms of the gas to form a plasma beam. Internal circle loop inductor 71 and external circle loop inductor 73, in which coils are wound, are disposed at an inner wall 82 and an outer wall 83 of the plasma channel 77, respectively. The internal circle loop inductor 71 and the external circle loop inductor 73 are coaxially arranged.
Hereinafter an operation of the plasma accelerating apparatus 60 will be described. When a gas is supplied to an inside of the plasma channel 77 from a gas source (not shown), the upper circle loop inductor 79 applies RF energy to the supplied gas to generate electrons. Consequently, the electrons collide with neutral atoms of the gas, and the gas is ionized to produce a plasma beam.
Referring to FIG. 4, the internal circle loop inductor 71 and the external circle loop inductor 73 induce a magnetic field B and a secondary electric current J in the plasma channel 77 to form an electromagnetic force F, which accelerates the plasma beam toward an outlet port 77a of the plasma channel 77. Moreover, the internal circle loop inductor 71 and the external circle loop inductor 73 are configured to reduce the number of turns of a coil wound therein, or to reduce an electric current flowing through a coil having the same number of turns along an axial direction. Accordingly, the magnetic field B, which is induced in the plasma channel 77, is reduced in an axial direction, and a drift velocity of the plasma beam toward an outlet port 77a of the plasma channel 77 is increased.
Since such a plasma accelerating apparatus 60 accelerates ions in the same direction regardless of a polarity of the electromagnetic force F, an anode electrode and a cathode electrode that the conventional electrostatic type accelerating apparatuses 10 and 40 must always include becomes unnecessary and, thus, leads to a simple construction thereof. Furthermore, the plasma accelerating apparatus 60 adjusts an electric current through the internal circle loop inductor 71 and the external circle loop inductor 73 that allows the generated electromagnetic force F to be adjusted in a simple manner.
However, in the plasma etcher or the sputtering system using the plasma accelerating apparatus 60, the etching rate for an etching or sputtering generation depends on ion energy and plasma density. The ion energy and the plasma density are influenced by not only an RF energy which is applied to an inside of the plasma channel 77 to generate the plasma beam, but also by an electromagnetic force F which accelerates the generated plasma beam toward the outlet port 77a of the plasma channel 77. Since the electromagnetic force F is induced with a magnetic field B and a second electric current J formed inside the plasma channel 77 by the internal circle loop inductor 71 and the external circle loop inductor 73, what is needed for an increase of the electromagnetic force F is to elevate a voltage applied to the internal circle loop inductor 71 and to the external circle loop inductor 73. However, because the a voltage applied to the internal circle loop inductor 71 and the external circle loop inductor 73 can not be increased without limit while maintaining operation efficiency, there is a limitation to increasing a drift velocity of the plasma beam by increasing the electromagnetic force F in order to increase the ion energy and the plasma density.
Furthermore, in order to enhance the accelerating efficiency of the plasma beam in the conventional plasma accelerating apparatus 60, the number of turns of the coils wound within the internal circle loop inductor 71 and the external circle loop inductor 73 is reduced in an axial direction, or an electric current flowing through the coils is reduced in an axial direction using the same number of turns of the coil, thereby causing the magnetic field B induced inside the plasma channel 77 to be reduced in the axial direction. However, in this case, the internal circle loop inductor 71 and the external circle loop inductor 73 should be separated from each other in an axial direction. Further, different electric currents must be applied to the internal circle loop inductor 71 and the external circle loop inductor 73 or the numbers of turns of the coils must be configured to be different from each other. As a result, it is difficult to manufacture the internal circle loop inductor 71 and the external circle loop inductor 73, and constructions thereof become complex.
Therefore, an improved plasma accelerating apparatus is needed, which may efficiently elevate a drift velocity of a plasma beam, thereby influencing a performance of a plasma etcher or a sputtering system, and which is simple to manufacture and simple in construction.